The present invention relates to a component carrier for plug-in modules equipped with front panels and including two parallel front module rails and two parallel rear module rails as well as equidistant, threaded holes arranged in a row along each front module rail for screwing on the front panels of the plug-in modules. Each front panel is provided with at least one fastening screw at the top and at the bottom and on its rear face with at least one centering pin in addition to the fastening screw.
The invention is used primarily in component carriers that are closed on all sides for which a very high shielding effect is required with respect to extraneous electromagnetic influences or which contain component groups from which electromagnetic radiation emanates that should not reach the outside or only to a very small degree.
The use of shielded, high frequency tight component carriers and the engineering measures taken in this connection are known. Housings for such components avoid as much as possible any parting grooves between the individual housing components or they are sealed with seals that provide electrical contacts. Problems arise in this connection from the unavoidable gaps between the plug-in modules that can be pushed into and out of such component carriers, whose front panels are in juxtaposition and form the front of the component carrier.
In order to seal the longitudinal gaps between the front panels of the plug-in modules, spring strips are known in various embodiments which, once the plug-in modules have been inserted, establish a plurality of electrical contacts with the longitudinal edges of the respectively adjacent front panels. The drawback is here that the establishment of the contacts and thus the shielding effect becomes considerably poorer after repeated insertion and removal of the plug-in module because the relatively sensitive contact springs are easily bent, exhibit fatigue or are damaged if they are jammed during insertion due to irregularities in the widths of the longitudinal gaps.
It is known to provide alignment pins in addition to fastening screws at the rear faces of the front panels in order to accurately maintain the widths of the longitudinal gaps between adjacent front panels of plug-in modules in component carriers. When the front panel is attached, these alignment pins engage in alignment holes provided at the module rails of the component carrier between the threaded holes for the fastening screws ("Futurebus+", P896.2: Physical Layer and Profile Specifications, Draft 5.497, 5,491, Jan. 22, 1991, Institute of Electrical and Electronic Engineers, Inc., New York, N.Y. 10017, USA). However, this system assumes that component carrier and plug-in module belong to the same standard and the spaces between the threaded holes and the alignment holes are subject to the same grid dimensions as the width of the front panels. Plug-in modules of other standards or front panels having a width that differs from the grid spacing cannot be employed. A particular drawback in this connection is the coarse grid spacing which permits no intermediate steps with respect to the widths of the front panels and is produced solely by the relatively large distance between two threaded holes, inevitably caused by the large alignment hole inserted therebetween.
Additionally, a component carrier for plug-in modules is known in which the front module rails are provided with screw strips for screwing on the front panels, with alignment pins projecting from the rear face of the front panel. These alignment pins are pressed into the threaded holes of the screw strips when the front panel is attached. In this connection it has been found, however, that after repeated insertion or exchange of the plug-in modules, the threads are damaged by the alignment pins and small metal chips are torn off which makes screwing on the front panels and their alignment more difficult (DE 90 10 410 U1).